Illuminator and illuminating method

ABSTRACT

An illumination device includes plural lamps a prism, a first lens array, and a second lens array, wherein the first lens array is formed such that images of the lamps are formed a predetermined space apart from each other on a lens, which corresponds to a predetermined lens among plural lenses of a second lens array, by light from the lamps having passed the predetermined lens of the first lens array. All or a part of plural images formed by a lens separate from the predetermined lens of the first lens array are practically arranged among the formed images of the lamps. And the second lens array is formed such that the images formed on the second lens array are irradiated on a light-receiving surface in a predetermined relation.

TECHNICAL FIELD

The present invention relates to an illumination device and anillumination method of illuminating, for example, a display device in aprojection display apparatus of projecting a large-screen image or thelike on a screen.

BACKGROUND ART

In recent years, as a projection video apparatus capable of performinglarge-screen display, various projection display apparatuses(projectors) using an optical modulation device have been attractingattention. These projection display apparatuses use light emitted from alight source serving as light generating means to illuminate a liquidcrystal of a transmission type or a reflection type or an opticalmodulation device, which can perform optical modulation, such as a DMD(digital micro-mirror device) which can change a reflection directionwith micro-mirrors arranged in array, form an optical image, whichcorresponds to a video signal supplied from the outside of the opticalmodulation device, on the optical modulation device, and enlarge andproject the optical image, which is illumination light modulated by theoptical modulation device, on a screen with a projection lens.

Examples of an important optical characteristic of a large screenprojected in this way include brightness and uniformity of thebrightness. It is important to condense light, which is generated from alamp serving as a light source, on an optical modulation device servingas a light-receiving surface and illuminate the optical modulationdevice with light beams having little unevenness of brightness. It hasbeen strongly requested to improve efficiency of an illumination deviceof illuminating the optical modulation device and make brightnessuniform.

In order to meet such a request, for example, an illumination device,which has a lens array constituted by irregular-shaped aperture lenses,has been proposed. FIG. 9 shows a structure of the illumination device.Beams of light emitted by a lamp 101 provided in a parabolic mirror 102are divided by a first lens array 110 in which lenses havingsubstantially the same shaped aperture are arranged two-dimensionally.Thereafter, the light reaches a light-receiving surface 106 via a secondlens array 112 which has lenses of the same number as the divided lightbeams, that is, the same number as the lenses of the first lens array110. In other words, the second lens array 112 is arranged such that thelight beams, which have reached thereto from a predetermined lens of thefirst lens array 110, pass through a corresponding lens on the secondlens array 112 to reach the light-receiving surface 106 (effectivearea). The divided light beams reach the light-receiving surface 106 andare superimposed one on top of another.

For example, FIG. 9 shows a state in which light passing through asecond lens from the above of the first lens array 110 passes through asecond lens from the above of the second lens array 112, which is in acorrespondence relation with the lens of the first lens array 110, andis irradiated on the light-receiving surface 106. The respective lightbeams divided by the first lens array 110 pass through respective lensesof the second lens array 112, which are in a correspondence relationwith the lenses of the first lens array 110, and are superimposed one ontop of another on the light-receiving surface 106. Thus, even if adistribution of luminance of light emitted from the lamp 101 is uneven,uniform brightness can be obtained on the light-receiving surface 106.

In addition, at this point, light substantially parallel with an opticalaxis made incident on the first lens array 110 is condensed by therespective lenses in the first lens array 110 and forms light sourceimages on the corresponding respective lenses of the second lens array.At this point, due to optical characteristics of the light source andthe parabolic mirror, light close to an optical axis 7 is focused as arelatively large image, and light distant from the optical axis 7 isfocused as a relatively small image on the second lens array 112.Therefore, as shown in FIG. 9, on the second lens array 112, lenses witha large aperture are arranged in the central part close to the opticalaxis, and lenses with a small aperture are arranged in the peripheralpart distant from the optical axis. Consequently, the lens arrayconstituted by the irregular-shaped aperture lenses as described aboveis adopted as the second lens array 112, whereby improvement ofefficiency of the illumination device can be realized.

In the above-described method, in order to further improve efficiency,an arrangement of the light source images formed on the second lensarray 112 is changed by adjusting (decentering) positions of center ofcurvature of the respective lenses in the first lens array 110. Forexample, in order to eliminate overlapping of light sources images inthe vicinity of the optical axis, the positions of center of curvatureof the respective lenses in the first lens array 110 are adjusted suchthat large useless spaces are eliminated by increasing spaces among thelight source images in the vicinity of the optical axis and decreasingspaces among the light source images in the peripheral part. Inaddition, on the second lens array 112, light overflowing from theapertures can be reduced by, for example, increasing sizes the aperturesthrough which light beams in the vicinity of the optical axis are passedwhile keeping sizes of the apertures through which light beams in theperipheral part are passed. Higher efficiency of use of light could beobtained by optimizing a shape of the second lens array such that therespective lenses in the second lens array 112 include the respectivelight source images in this way (e.g., see Japanese Patent Laid-Open No.05-346557). FIG. 10 shows an example of an image which is formed on thesecond lens array 112 obtained as described above.

In addition, as shown in FIG. 11, there is also an illumination systemwith which high efficiency can be obtained by using plural light sources(e.g., see Japanese Patent Laid-Open No. 2000-171901). In this case, thesecond lens array 112 is not formed in an optimal shape as described inJapanese Patent Laid-Open No. 05-346557, but a second lens array (withapertures of the same shape) having substantially the same shape as thefirst lens array 110 is used.

Also, in a constitution described in Japanese Patent Laid-Open No.2000-171901, and in a constitution in which a method of synthesizingplural light sources described in Japanese Patent Laid-Open No.2000-171901 is applied to a constitution described in Japanese PatentLaid-Open No. 05-346557, as in the case in which the single light sourceis used, light source images formed in the central part of the lensarray 112 are light source images which are large compared with lightsource images formed in the peripheral part. This phenomenon will behereinafter described with reference to FIG. 11.

Since an ellipsoidal mirror 2 has a focusing action like a lens, lightbeams irradiated from a light-emitting portion 16 of a first focus 15are condensed in the vicinity of a second focus 17 to form an image ofthe light-emitting portion 16 on the second focus 17 side on a prism 4.However, an action of the ellipsoidal mirror 2 is different from anaction of a lens in the following point. That is, if a lens is usedinstead of using the ellipsoidal mirror 2, in the case of the lens, aratio of a distance from a position of the light-emitting portion 16 toa lens surface having the focusing action and a distance from the lenssurface to a position, where an image is focused, is always fixedwhichever position of the lens light passes On the other hand, in thecase in which the ellipsoidal mirror 2 is used, if a distance from thefirst focus 15, where the light-emitting portion 16 of the lamp 1 isarranged, to a reflection surface of the ellipsoidal mirror 2 having thefocusing action is short, a distance from a position of the reflectionsurface to a second focus 17, where a light source image is formed, islong. In such a case, a relatively large light source image is formed onthe second focus 17 side on the prism 4. Conversely, as the distancefrom the first focus 15 to the reflection surface of the ellipsoidalmirror 2 becomes longer, the distance from the reflection surface of theellipsoidal mirror 2 to the second focus 17 becomes shorter. In such acase, a relatively small light source image is formed on the secondfocus 17 side.

Therefore, in the optical system shown in FIG. 11, when a light beamirradiated from the light-emitting portion 16 of the lamp 1 is reflectedin the vicinity of the optical axis of the ellipsoidal mirror 2, thedistance from the reflection surface of the ellipsoidal mirror 2 to thesecond focus 17 side on the prism 4 becomes relatively long. Asindicated by a single arrow in FIG. 11, a light beam made incident on asynthesis mirror 6 of the prism 4 through such a path has a largeoutgoing angle and is made incident in the vicinity of an optical axisof a lens 8. As a result, this light beam passes through a lens 109 inthe vicinity of the optical axis 7 of the first lens array 110 andfocuses a relatively large light source image on a lens 111 in thecentral part of the second lens array 112.

On the other hand, when a light beam irradiated from the light-emittingportion 16 of the lamp 1 is reflected in a position distant from theoptical axis of the ellipsoidal mirror 2, the distance from thereflection surface of the ellipsoidal mirror 2 to the second focus 17side on the prism 4 becomes relatively short. As indicated by a doublearrow in FIG. 11, the light beam made incident on the synthesis mirror 6of the prism 4 through such a path has a small outgoing angle and ismade incident in a position distant from the optical axis of the lens 8.As a result, this light beam passes through the lens 109 distant fromthe optical axis of the first lens array 110 and focuses a relativelysmall light source image on the lens 111 in the peripheral part of thesecond lens array 112. Note that the above description is true for alamp 1′ and an ellipsoidal mirror 2′.

In this way, on the second lens array 112, relatively large two lightsource images are formed in the central part and relatively small twolight source images are formed in the peripheral part. In addition,since a size of the light source image is different in the central partand the peripheral part, there is almost no space or there is a smallspace between two light source images on the second lens array 112 inthe central part, but a relatively large space is formed in theperipheral part. FIG. 12 shows an example of a light source image on thesecond lens array formed as described above. FIG. 12 shows an example inwhich there are thirty-six lenses 9, there are two light sources, andseventy-two light source images are formed on the lens array 12.

In the illumination optical system using the first lens array 110 andthe second lens array 112, only in the case in which a light sourceimage condensed in the respective lenses 109 has passed through theapertures of the corresponding respective lenses 111 of the second lensarray 112, the light source image is irradiated on an area, which shouldbe illuminated, as an effective light beam. Therefore, in order toincrease light beams which are irradiated on an area which should beilluminated, as in the case of the single light source, it isconceivable to increase a size of the apertures of the respective lenses111 in the central part of the second lens array 112.

In addition, in another optical system, in the case in which an opticalsystem of separating two polarized components inherent in natural lightis arranged between the first lens array 110 and the second lens array112 even if one light source is used, or in an optical system of makingtwo optical axis substantially agree with each other by the time whenlight beams reach the second lens array 112 after the light beams areemitted from two light sources and reach the separate lens arrays 110,compared with the number of lenses NLA1 included in the first lens array110, the number of lenses NLA2 included in the second lens array 112 ismade equal to a number found by multiplying the number of light beamsfrom one light source, which is divided by a polarized component or awavelength band, or the number of light source N=2 by the number oflenses NLA1 of the first lens array as indicated by the followingexpression,NLA 2=2×NLA 1  (Expression 1)whereby an illumination device using plural light beams or light sourcesis constituted (e.g., see Japanese Patent Laid-Open No. 11-66926 andJapanese Patent No. 3301951).

However, when plural light sources are provided and the second lensarray is provided with regular-shaped apertures or irregular-shapedapertures, since a gap exists between a pair of light source imagesformed on lenses in the peripheral part of the second lens array 112,there is a problem in that further improvement of efficiency cannot beattained. In this case, if a light source image, which is formed by alens separate from the predetermined lens 109 of the first lens array110, is arranged in the gap between this pair of light source images,since a light beam of a light source image, which is formed by theseparate lens 109′, inserted between the pair of light source images isnot condensed in an area which should be illuminated from the secondlens array, after all, efficiency of use of the illumination device isdeclined.

This will be hereinafter described specifically. FIG. 13 shows anarrangement of images of two light sources on the second lens array 112in the case in which irregular-shaped aperture lenses are used as thesecond lens array 112. As it is evident from FIG. 13, compared withlight source images in the central part, light source images in theperipheral part of the second lens array are small images with spacesformed among the images.

FIG. 14(a) shows paths of light beams passing through the first lensarray 110 and the second lens array 112 to reach the light-receivingsurface 114 in the case in which irregular-shaped aperture lenses areused as the second lens array 112. Light having passed through apredetermined lens 109 of the first lens array 110 reaches the entirelight-receiving surface 114 serving as an area, which should beilluminated (an effective area shown in FIG. 14(a)), via the lens 111 onthe second lens array 112 corresponding to the lens 109. Then,similarly, light having passed through separate predetermined lens 109′of the first lens array 110 reaches the entire light-receiving surface114 serving as an area, which should be illuminated, via a lens 111′corresponding to the lens 109′.

Next, it is considered to arrange another pair of light source images inorder to make use of the gap between the pair of light source images inthe peripheral part of the lens array 112 shown in FIG. 13. As shown inFIG. 14(b), the decentering of the lens 109′ is adjusted so as to causea light beam having passed through the lens 109′ of the first lens array110 to reach the lens 111 instead of reaching the lens 111′.

In other words, the decentering of the lens 109′ is adjusted so as toinsert at least one light source image of a pair of light source images,which are condensed by the lens 109′ separate from the predetermine lens109 on the lens array 110, between a pair of light source imagescondensed by the predetermined lens 109 of the lens array 110.Therefore, at this point, the lens 111, which is one aperture having onecenter of curvature, includes at least three light source images.

The center of curvature of the lens 111 in the second lens array 112 isset so as to irradiate a light beam having passed through the lens 109of the first lens array 110 on the light-receiving surface 114 via thelens 111. Therefore, a light beam, which passes through the lens 109′ toreach the lens 111 having a correspondence relation with the lens 109,cannot reach the entire light-receiving surface 114 serving as an areawhich should be illuminated (effective area). In other words, the lightbeam reaches an ineffective area shown in FIG. 14(b). Due to suchreasons, with the conventional design method and constitution ofdecentering the first lens array 110 such that a light source imageformed by the lens 109′ separate from the predetermined lens 109 of thefirst lens array 110 is arranged in a gap of light source images formedby the predetermined lens, efficiency of use of the illumination deviceis declined on the contrary.

Note that the lenses included in the second lens array 112 in FIG. 14and the lenses included in the second lens array 112 shown in FIG. 9 areshown in the figure in different numbers and shapes. However, this doesnot relate to the essence of the description.

The constitutions described in Japanese Patent Laid-Open No. 05-346557and Japanese Patent No. 3301951 have the same problems as theabove-described examples. Note that the entire disclosure of theabove-described documents is incorporated herein by reference in itsentirety.

DISCLOSURE OF THE INVENTION

In view of the above-described problems, it is an object of the presentinvention to provide an illumination device and an illumination methodwhich can improve efficiency of use of plural light sources.

According to the present invention, an illumination device and anillumination method, which can improve efficiency of use of plural lightsources, can be provided.

The 1^(st) invention of the present invention is an illumination devicecomprising:

-   -   plural light sources;    -   reflecting means having a reflection surface of reflecting        light, which is irradiated from said plural light sources, in        predetermined directions in association with the respective        light sources;    -   a first lens array having plural lenses which is arranged a        predetermined space apart from said reflecting means; and    -   a second lens array having plural lenses which is arranged a        predetermined space apart from said first lens array,    -   wherein said first lens array is formed such that images of said        plural light sources are formed a predetermined space apart from        each other on lenses, which corresponds to a predetermined lens        of said first lens array, among the plural lenses of said second        lens array by light from said plural light sources having passed        the predetermined lens of said first lens array, and all or a        part of plural images formed by another lens different from said        predetermined lens of said first lens array are arranged        substantially among said formed images of said plural light        sources, and    -   said second lens array is formed such that light beams forming        light sources images on said second lens array illuminate a        light-receiving surface in a predetermined relation.

The 2^(nd) invention of the present invention is the illumination deviceaccording to the 1^(st) invention of the present invention,

-   -   wherein said another lens of said first lens array is formed to        be decentered such that all or a part of plural images formed by        said another lens are arranged among plural images formed on        said second lens array by the predetermined lens of said first        lens array.

The 3^(rd) invention of the present invention is the illumination deviceaccording to the 2^(nd) invention of the present invention,

-   -   wherein said second lens array is formed such that the images        formed on said second lens array via said another lens of said        first lens array are guided to an area, which is to be        illuminated, of said light-receiving surface.

The 4^(th) invention of the present invention is the illumination deviceaccording to the 3^(rd) invention of the present invention,

-   -   wherein said second lens array is formed without a center of        curvature of lenses, on which the images formed via said another        lens of said first lens array are formed, on said second lens        array being changed substantially.

The 5^(th) invention of the present invention is the illumination deviceaccording to the 4^(th) invention of the present invention,

-   -   wherein the plural lenses, on which the images formed via said        another lens of said first lens array, on said second lens array        are arranged across at least one lens on which the images formed        via said predetermined lens of said first lens array.

The 6^(th) invention of the present invention is the illumination deviceaccording to the 5^(th) invention of the present invention,

-   -   wherein said plural light sources comprise a first light source        and a second light source,    -   said second lens array includes a first lens, a second lens, a        third lens, and a fourth lens,    -   the first lens and the third lens of illuminating images, which        have passed through the predetermined lens of said first lens        array, on said light-receiving surface are formed on said second        lens array,    -   the second lens and the fourth lens of illuminating images,        which have passed through said another lens of said first lens        array, on said light-receiving surface are formed on said second        lens array,    -   a center of curvature of said first lens and a center of        curvature of said third lens substantially coincide with each        other to form a first center of curvature, and a center of        curvature of said second lens and a center of curvature of said        fourth lens substantially coincide with each other to form a        second center of curvature different from said first center of        curvature, and    -   said first lens, said second lens, said third lens, and said        fourth lens are arranged in this order.

The 7^(th) invention of the present invention is the illumination deviceaccording to the 1^(st) invention of the present invention

-   -   wherein, in said second lens array, an aperture of a lens close        to an optical axis is formed larger than an aperture of a lens        distant from the optical axis, and an aperture of a lens distant        from the optical axis is formed smaller than an aperture of a        lens close to the optical axis.

The 8^(th) invention of the present invention is the illumination deviceaccording to the lt invention of the present invention,

-   -   wherein said first lens array is formed such that, in a first        predetermined space which is a largest space of spaces among        plural images formed on said second lens array by the        predetermined lens of said first array, a largest image among        images formed on said second lens array with a second        predetermined space, which is smaller than said first        predetermined space, apart from each other by said another lens        of said first lens array is arranged.

The 9^(th) invention of the present invention is the illumination deviceaccording to the 8^(th) invention of the present invention,

-   -   wherein said plural light sources comprise a first light source        and a second light source, and    -   said first lens array is formed such that a value obtained by        dividing a width of an image according to a first light source,        which is formed by the predetermined lens of said first lens        array, by said second predetermined space is equal to or larger        than a value found by dividing a width of an image according to        a second light source, which is formed by said another lens of        said first lens array, by said first predetermined space.

The 10^(th) invention of the present invention is the illuminationdevice according to the 1^(st) invention of the present invention,further comprising a display device of providing video information,which is arranged a predetermined space apart from said second lensarray, between said second lens array and said light receiving surface.

The 11^(th) invention of the present invention is an illumination methodcomprising:

-   -   a step of reflecting light irradiated from plural light sources        in predetermined directions with reflecting means in association        with the respective light sources and guiding the light to a        first lens array having plural lenses which is arranged a        predetermined space apart from said reflecting means;    -   a second lens array having plural lenses which is arranged a        predetermined space apart from said first lens array;    -   a step of guiding the light from said plural light sources,        which has passed through a predetermined lens of said first lens        array, onto a lens corresponding to said predetermined lens        among plural lenses of a second lens array having plural lenses        which is arranged a predetermined space apart from said first        lens array and forming images of said plural light sources with        a predetermined space apart from each other;    -   a step of forming said first lens array such that all or a part        of plural images, which are formed by another lens different        from said predetermined lens of said first lens array, are        arranged substantially among said formed images of said plural        light sources; and    -   a step of forming said second lens array such that images formed        on said second lens array are illuminated on a light-receiving        surface in a predetermined relation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an illumination device of an embodimentof the present invention;

FIG. 2(a) is a plan view showing an example of a shape of a second lensarray of the illumination device of the embodiment of the presentinvention;

FIG. 2(b) is a sectional view showing the example of the shape of thesecond lens array of the illumination device of the embodiment of thepresent invention;

FIG. 3(a) is a plan view of a lens array which is used in theillumination device of the embodiment of the present invention;

FIG. 3(b) is a plan view of a lens array which is used in theillumination device of the embodiment of the present invention;

FIG. 3(c) is a plan view of a lens array which is used in theillumination device of the embodiment of the present invention;

FIG. 3(d) is a plan view of a lens array which is used in theillumination device of the embodiment of the present invention;

FIG. 4 is a schematic diagram showing a determination method for anarrangement of light source images of the illumination device of thepresent invention;

FIG. 5(a) is a plan view showing an example of a shape of a second lensarray of the illumination device of the embodiment of the presentinvention;

FIG. 5(b) is a sectional view showing the example of the shape of thesecond lens array of the illumination device of the embodiment of thepresent invention;

FIG. 6(a) is a plan view showing an example of a shape of the secondlens array of the illumination device of the embodiment of the presentinvention;

FIG. 6(b) is a sectional view showing the example of the shape of thesecond lens array of the illumination device of the embodiment of thepresent invention;

FIG. 7 is a plan view showing an example of the shape of the second lensarray of the illumination device of the embodiment of the presentinvention;

FIG. 8 is a schematic diagram showing one constitutional example of theillumination device of the embodiment of the present invention;

FIG. 9 is a schematic diagram showing a structure of a conventionalillumination device having irregular-shaped aperture lenses;

FIG. 10 is a schematic diagram showing an example of light sourcesimages which are focused on a second lens array of the conventionalillumination device having irregular-shaped aperture lenses;

FIG. 11 is a schematic diagram showing a structure of a conventionalillumination device having plural light sources;

FIG. 12 is a schematic diagram showing an example of plural light sourceimages which are focused on a second lens array of the conventionalillumination device having plural light sources;

FIG. 13 is a schematic diagram showing an example of plural light sourceimages which are focused on a second lens array of a conventionalillumination device having plural light sources and havingirregular-shaped aperture lenses;

FIG. 14(a) is a schematic diagram illustrating an operation principle ofthe conventional illumination device having irregular-shaped aperturelenses; and

FIG. 14(b) is a schematic diagram illustrating an operation principle ofthe conventional illumination device having irregular-shaped aperturelenses.

DESCRIPTION OF REFERENCE NUMERALS

-   1, 1′ Lamps-   2, 2′ Ellipsoidal mirrors-   3, 3′ Lamp units-   4 Prism-   5 Illumination unit-   6, 6′ Synthesis mirrors-   7 Optical axis-   8, 9, 11, 13 Lenses-   10, 12 Lens arrays-   14 Light-receiving surface-   15, 15′ First focuses-   16, 16′ Light-emitting portions-   17, 17′ Second focuses-   18 Side

BEST MODE FOR CARRYING OUT THE INVENTION

A structure and an operation of an illumination device of an embodimentof the present invention will be hereinafter described with reference tothe drawings. FIG. 1 shows a schematic structure of the illuminationdevice in accordance with the embodiment of the present invention.

The illumination device of this embodiment is constituted by including:two lamp units 3 as an example of plural light sources of the presentinvention which include lamps 1 and ellipsoidal mirrors 2 serving ascondensing means; a triangular prism 4 as an example of reflecting meansof the present invention, a side 18 of which is coated with a reflectionfilm to form a synthesis mirror 6 as an example of a reflection surfaceof the present invention; a lens 8 which is arranged a predeterminedspace apart from the prism 4 and changes light beams, which areirradiated from the lamp units 3 and reflected on the synthesis mirror6, to light beams substantially parallel to an optical axis of anillumination unit 5; a lens array 10 as an example of a first lens arrayof the present invention which is set a predetermined space apart froman outgoing side of the lens 8 and has a shape with plural lenses 9arranged in a two-dimensional shape; a lens array 12 as an example of asecond lens array of the present invention which is arranged apredetermined space apart from an outgoing side of the lens array 10 andhas a shape with plural lenses arranged in a two-dimensional shape; alens 13 which is arranged a predetermined space apart from an outgoingside of the lens array 12 and is used for irradiating a light beamemitted from the lens array 12 on a light-receiving surface; and alight-receiving surface 14 which is arranged a predetermined space apartfrom the lens 13 and is used for irradiating a light beam emitted fromthe lens 13.

As the lamp 1, a very high pressure mercury lamp in which alight-emitting material such as mercury or inert gas is enclosed in aglass tube and a pressure in the glass tube at the time of lightingrises to a very high pressure or, other than the very high pressuremercury lamp, a lamp such as a metal halide lamp, a xenon lamp, or ahalogen lamp excellent in light-emitting efficiency is used.

A light-emitting portion 16 of the lamp 1 is arranged in a first focus15, which is one focus of the ellipsoidal mirror 2 and condenses lightirradiated from the lamp 1 on a second focus 17 side which is anotherfocus of the ellipsoidal mirror 2. A mirror surface of the synthesismirror 6 is arranged in the vicinity of the second focus 17 of thisellipsoidal mirror 2 and can reflect light emitted from the ellipsoidalmirror 2 in a direction of the illumination unit 5. Similarly, lightirradiated from the lamp 1′ of the other ellipsoidal mirror 2′, which isarranged to be opposed to one ellipsoidal mirror 2, is also condensed bythe other ellipsoidal mirror 2′ and then reflected in a predetermineddirection on a mirror surface of the other synthesis mirror 6′ of theprism 4. Consequently, the light irradiated from the two lamps 1 and 1′is made incident on the illumination unit 5 as light beams traveling insubstantially the same direction.

The light emitted from the ellipsoidal mirrors 2 and 2′ in the vicinityof the synthesis mirrors 6 and 6′ is condensed in small light sourceimages in the vicinity of the second focuses 17 and 17′ and travelsexpanding to the illumination unit 5 side with the vicinity of thereflection surfaces of the synthesis mirrors 6 and 6′ as start points.The light traveling while expanding in this way is made incident on thelens 8 and is converted into light beams substantially parallel with theoptical axis 7 of the illumination unit 5 to exit from the lens 8.

The light beams having exited from the lens 8 are guided into the plurallenses 9 of the lens array 10 and divided into partial light beams. Thedivided respective partial light beams are focused on the lens array 12,which has lenses corresponding to the respective lenses in the lensarray 10, in shapes similar to apertures of the respective lenses andsuperimposed one on top of another on the light-receiving surface 14serving as an area, which should be illuminated, via the lens 13.Consequently, although unevenness of brightness exists in the lightbeams at the point when the light beams are made incident on the lensarray 10, the respective partial light beams having various luminancedistributions are superimposed one on top of another, wherebyillumination with high uniformity is realized in the area which shouldbe illuminated.

The lens array 10 and the lens array 12 are arranged a space apart fromeach other such that the partial light beams divided by the lens array10 are condensed in the vicinity of the lens array 12. In addition, inthe optical system shown in FIG. 1, since there is one light sourceimage formed on the synthesis mirrors 6 and 6′, respectively, therespective partial light beams condensed by the respective lenses 9 alsoform two light source images.

Therefore, light source images of a number, which is found bymultiplying the number of lenses 9 included in the lens array 10 by thenumber of light source images formed on the synthesis mirror 6 and thesynthesis mirror 6′, are formed on the lens array 12.

In the illumination device of the embodiment of the present invention,lenses in the peripheral part among the lenses of the lens array 12 aredivided so as to efficiently include the respective light source images.In addition, as shown in FIG. 1, the lenses 9′ which constitute the lensarray 10, are arranged to be decentered such that light source imagesare formed on the divided lenses of the lens array 12. In other words,for example, in the example shown in FIG. 1, the lens 9, is decenteredsuch that two light source images from the lens 9 of the lens array 10are formed as light source images 27 and 29 on a lens 21, which is anexample of a first lens of the present invention, and a lens 23, whichis an example of a third lens of the present invention, of the lensarray 12, respectively, and two light source images from the lens 9′separate from the lens 9 are formed as light source images 28 and 30 ona lens 22, which is an example of a second lens of the presentinvention, and a lens 24, which is an example of a fourth lens of thepresent invention, of the lens array 12, respectively.

According to the related art, the light source image corresponding tothe lens 9 is formed on a lens 11 (a lens having an area consisting ofthe lenses 21, 22 and 23 are assumed and called in this way) of the lensarray 12, and the light source image corresponding to the lens 9′ isformed on a lens 11′ (a lens having an area consisting of the lenses 22,23 and 24 and not overlapping the area of the lens 11 is assumed andcalled in this way) of the lens array 12. The division of the lens array12 means that the lens 11 is divided into the lenses 21, 22 and 23 andthe lens 11′ is divided into the lenses 22, 23 and 24 as describedabove.

The lenses of the lens array 12 are divided in this way to be arrangedsuch that one light source image is placed between the other lightsource images, whereby an area of the peripheral part on the lens array12 can be reduced (e.g., to 4/6) compared with the second lens array 112of the related art.

Such a concept of the lens division in the lens array 12 is illustratedmore specifically in FIGS. 2(a) and (b). In short, as shown in FIGS.2(a) and (b), the apertures of the lenses in the peripheral part of thelens array 12 are divided into the lens 21 and the lens 23, which areapertures corresponding to a light source image from the predeterminedlens 9 of the lens array 10, and the lens 22 and the lens 24, which areapertures corresponding to a light source image from separate lens 9′other than the predetermined lens 9. Then, the lens 21, the lens 22, thelens 23, and the lens 24 are arranged in this order. In addition, acenter of curvature 25, which is an example of a first center ofcurvature of the present invention, of the lens 21 and the lens 23 and acenter of curvature 26, which is an example of a second center ofcurvature of the present invention, of the lens 22 and the lens 24 arearranged to be adjacent to but deviated from each other. In other words,a center of curvature of the lens 21 and a center of curvature of thelens 23 substantially agree with each other to form the center ofcurvature 25, and a center of curvature of the lens 22 and a center ofcurvature of the lens 24 substantially agree with each other to form thecenter of curvature 26. The center of curvature 25 and the center ofcurvature 26 are arranged to be deviated from each other.

The center of curvature 25 of the lenses 21 and 23 agrees with a centerof curvature of the lens 11. In addition, the center of curvature 26 ofthe lenses 22 and 24 agrees with a center of curvature of the lens 11′.In other words, the centers of curvature of the lenses 11 and 11′ areformed without being changed substantially regardless of whether thelenses 11 and 11′ are divided or not (i.e., substantially preservedbefore and after the division of the lenses 11 and 11′). In other words,the centers of curvature 25 and 26, in the case in which the lenses 11and 11′ are divided, are formed to agree with the center of curvature inthe case in which the lenses 11 and 11′ are not divided.

FIG. 2(a) shows a plan view of such lenses 21 to 24 formed on the lensarray 12, and FIG. 2(b) shows a sectional view thereof. With such aconstitution, individual light source images condensed by the lens 9pass through the lenses 21 and 23 having the center of curvature 25, andindividual light source images condensed by the lens 9′ pass through thelenses 22 and 24 having the center of curvature 26. The light sourceimages are efficiently irradiated as effective light beams on thelight-receiving surface 14 serving as an area which should beilluminated.

In this way, the lenses in the peripheral part of the lens array 12, inwhich a large gap tends to be formed between a pair of light sourceimages formed by the lens 9 of the lens array 10, are divided, and pairsof the divided lenses have predetermined centers of curvature,respectively. Thus, a gap between light source images formed on the lensarray 12 can be reduced, and the light source images can be includedmore efficiently with a small aperture than in the past.

For example, in the conventional illumination device, the light sourceimages 27 and 29 are focused in the area formed of the lenses 21, 22 and23 on the lens array 12, and the light source images 28 and 30 arefocused in the area formed of the lenses 22, 23 and 24 which is an areaseparate form the area in which the area of the lenses 21, 22 and 23 isformed. Therefore, when it is assumed that areas of the lenses 21 to 24are identical, in order to focus a light source image from thepredetermined lens 9 and a light source image from the separate lens 9′on the lens array 12, an area equivalent to six lenses 21 is required.

However, according to the illumination device of the present invention,with an area equal to four lenses 21, a light source image from thepredetermined lens 9 and a light source image from the separate lens 9′can be focused on the lens array 12. Therefore, it is possible to causean area, which can be saved in the peripheral part of the lens array 12,to contribute to an increase in apertures of the lenses in the centralpart of the lens array 12. Alternatively, by reducing the area in theperipheral part of the lens array 12 as described above, an area of theentire lens array 12 can be made smaller than the conventionalirregular-shaped aperture lenses, and miniaturization of theillumination device itself can also be realized.

Note that the example shown in FIGS. 2(a) and (b) is an example. Inparticular, concerning the centers of curvature 25 and 26, arrangementsother than the illustration are naturally conceivable.

In the illumination device of the present invention, parts (gaps) on thelens array 12, where light source images are not arranged, areeliminated as much as possible, and a filling factor of light sourceimages on the lens array 12 is increased, whereby an illumination systemwith higher efficiency can be realized by a smaller optical system.

In this way, efficiency of the illumination device can be improved morewhen the lenses arranged in the peripheral part of the lens array 12 aredivided and the number of lenses of the lens array 12 is increased.

However, when the number of lenses of the lens array 12 is increasedwithout any limitation, even if a light source image formed by theseparate lens 9′ is moved to between a pair of light source imagesformed in the central part of the lens array 12, since a light sourceimage in the vicinity of the optical axis is large, there is no gapbetween the pair of light source images, and there is almost no placefor arranging the new light source image. In other words, on the lensesin the central part of the lens array 12, most of light source imagesformed by the separate lens 9′ overlap the existing light source images.In this case, since a position of a center of curvature of the lenseshas to be associated with one of the lenses 9 and 9′, any one of thelight source images in the overlapping part of the light source imagesdoes not reach an area which should be illuminated, which leads to aloss in terms of illumination efficiency.

Therefore, in order to obtain the above-described effects more surely,the number of lenses NLA2 of the lens array 12 only has to satisfy thefollowing relation with respect to the number of lenses NLA1 of the lensarray 10:NLA 1 <NLA 2<2×NLA 1  (Expression 2)

Shapes of the lens array 10 and the lens array 12 may be any shapes aslong as the above (expression 2) is satisfied. As such an example, FIG.3(a) shows an example of a shape of the lens array 10 in the case inwhich the number of the lenses 9 is forty-eight, and FIG. 3(b) shows anexample of a shape of the lens array 12, which has sixty lenses,corresponding to the lens array 10 shown in FIG. 3(a). In addition, FIG.3(c) shows an example of a shape of the lens array 10 in the case inwhich the number of the lenses 9 of the lens array 10 is forty-two.Further, FIG. 3(d) shows an example of a shape of the lens array 12,which has forty-six lenses, corresponding to the lens array 10 shown inFIG. 3(c) A part of the lenses of the lens array 12 is divided in thisway, whereby a size of the entire lens array 12 can be reduced to makethe entire illumination device small, or sizes of the apertures of thelenses in the central part of the lens array 12 can be further increasedso much more for the reduction of a gap between the pair of light sourceimages formed in the peripheral part of the lens array 12. Thus, itbecomes possible to improve efficiency of use of light.

Next, it will be explained, when at least one light source image of apair of light source images, which are formed by the lens 9′ separatefrom the predetermined lens 9 of the lens array 10, is arranged betweena pair of light source images formed by the predetermined lens 9 of thelens array 10, which of the pair of light source images formed by theseparate lens 9′ should be moved to a gap between the pair of lightsource images formed by the predetermined lens 9.

FIG. 4 and FIG. 5 show examples in which light source images, which areactually formed in the peripheral part of the lens array 12, are used.As shown in FIG. 4, it is assumed that, in a pair of light source imagesformed by the one predetermined lens 9, a width of a large light sourceimage on a straight line connecting area centers of the respective lightsource images is R1, a width of a smaller light source image is L1, anda width of a gap between the light source images is G1, and similarly,widths of a pair of light source images formed by the separate lens 9′(i.e., light source images which would be originally formed on animaginary lens 11′ on the lens array 12 corresponding to the lens 9′ inthe case in which the lens 9′ is assumed not to be decentered) are R2and L2, and a width of a gap between these light source images is G2. Inthe case in which such two pairs of light source images are combined,efficiency is better when the images are arranged such that a rate ofthe width (R1 or R2) of the large image with respect to the width (G1 orG2) of the gap between the respective light source images is as small aspossible.

In other words, the arrangement among the respective light source imagesonly has to be determined such that the following relation is satisfied:R2/G1≧R1/G2  (Expression 3)

For example, in the examples shown in FIG. 4 and FIG. 5, efficiency isbetter with a constitution in which, rather than inserting a lightsource image 38 having the width L2 in the gap of G1 or inserting alight source image 37 having the width L1 in the gap of G2, a lightsource image 39 having the large width R1 larger than a light sourceimage 40 having the width R2 is inserted in the gap of G2 larger thanG1.

For example, FIG. 5(a) two-dimensionally shows a part of a structure ofthe lens array 12 in the case in which the light source image 38 isarranged between the light source images 37 and 39 and FIG. 5(b) shows asection thereof. Although a lens 31 and a lens 33 are different lenses,these lenses have an identical center of curvature and are arrangedacross a lens 32. Further, although the lens 32 and a lens 34 aredifferent lenses, these lenses have an identical center of curvature andare arranged across the lens 33. In this case, the center of curvatureformed by the lenses 31 to 33 and the center of curvature formed by thelenses 32 to 34 are arranged to be adjacent to but deviated from eachother.

However, even in the case in which the above-described arrangement isnot adopted, the same effect as described above can be obtained in thatefficiency can be made higher than the conventional method and a size ofthe illumination device can be reduced.

In addition, in the case in which a gap between a pair of light sourceimages is large, and a small light source image formed by the separatelens 9′ is inserted in the gap between the light source images, aconstitution for inserting two or more pairs of light source imagesformed by plural separate lenses 9′ or the like rather than a pair oflight source images may be adopted. In this case, again, the respectivelenses after division of the lens array 12 are arranged with positionsof centers of curvature thereof adjacent to but deviated from each otherin an area included in the lens 11, through which the pair of lightsource images pass, such that light beams from the corresponding lenses9 and 9′ or the like become effective illumination reaching an areawhich should be illuminated. In addition, the lenses 9 and 9′ or thelike are arranged to be decentered such that light beams passing throughthe lenses or the like are condensed by the lens 11.

For example, FIG. 6(a) shows, as a plan view, a part of a structure ofthe lens array 12 in the case in which a light source image 51 and alight source image 52 are arranged between light source images 50 and53, and FIG. 6(b) shows a section thereof. In this case, a center ofcurvature 47 is formed by lenses 41 to 44, a center of curvature 48 isformed by lenses 42 to 45, and a center of curvature 49 is formed bylenses 43 to 46. The centers of curvature 47, 48 and 49 are arranged tobe adjacent to but deviated from each other.

In other words, a center of curvature of the lens 41 and a center ofcurvature of the lens 44 substantially agree with each other to form thecenter of curvature 47, a center of curvature of the lens 42 and acenter of curvature of the lens 45 substantially agree with each otherto form the center of curvature 48, and a center of curvature of thelens 43 and a center of curvature of the lens 46 substantially agreewith each other to form the center of curvature 49. The centers ofcurvature 47, 48 and 49 are arranged to be deviated from each other.However, the respective centers of curvature are formed without changeregardless of whether the lens 11 is divided or not as in the case shownin FIGS. 2(a) and (b).

In this way, the lens array 10 and the lens array 12 are formed so as tofill a gap between light source images with another light source imageas much as possible, whereby a distance among the respective centers ofcurvature formed on the predetermined lens 11 on the lens array 12 canbe reduced. Therefore, in that case, the size of the entire lens array12 can be further reduced, or a diameter in the central part of the lensarray 12 can be increased, whereby efficiency of use of light can beimproved.

In addition, as shown in FIG. 7, in the lenses after division of thelens array 12, in the case in which one pair of light source imagesamong two pairs of light source images are relatively small and do notcontribute to overall efficiency of use of light significantly, the lens11 may be constituted by three or two of four lenses 11.

As described above, according to the present invention, the lens array12 is divided to be smaller than the lens array 10, whereby gap areas,which are generated among plural light source images formed on the lensarray 12, can be reduced, and an illumination device with highefficiency of use of light can be obtained. In addition, if theillumination device of the present invention is used, a projectiondisplay device with high efficiency of use of light can be realized.

Note that outward forms, which are illustrated for representing sizes oflight source images shown in FIGS. 12 and 2(a), are indicated byequi-luminance lines having luminance of 10 to 30% in the case in whicha maximum luminance in the light source image is assumed to be 100%.Such equi-luminance lines are indicators indicating a range in whichefficiency of use of light is affected by taking in light as a lightsource image in the aperture of the lens 11. Thus, by the aboveformation of the lens arrays 10 and 12 in the case in which all theoutward forms of these equi-luminance lines are contained in the lens11, a significant effect can be obtained by using the above-describedmethod. However, even in the case in which the outward forms of theequi-luminance lines partly overlap each other, or even in the case inwhich a part of the outward forms of the equi-luminance lines bulges outfrom the lens 11, it is possible that effects such as improvement ofefficiency and reduction in a size of the lens array 12 can be obtainedas the optical system as a whole.

In addition, a gap or a space between plural light source images in theabove description have been represented as a distance from oneequi-luminance line to another equi-luminance line on a line connectingarea centers of images surrounded by the equi-luminance lines. However,the space between the light source images may be defined by othermethods.

Further, in the above description, the triangular prism 4 having thesynthesis mirrors 6 and 6′, the sides of which are coated with areflective film, is described as the reflecting means of the presentinvention. However, the reflecting means of the present invention is notlimited to the prism 4 but may be a structure using two mirrors and maybe any structure as long as the structure reflects light beamsirradiated from two light sources to the illumination unit 5.

Moreover, in the above description, the example of using the ellipsoidalmirror 2 as the condensing means is described. However, the condensingmeans may be a parabolic mirror. Furthermore, it is also conceivablethat a lens is used as the condensing means. In that case, since a sizeof a light source image does not change significantly in the centralpart and the peripheral part of the second lens array 12, a shape of thelens array 12 is not required to be irregular-shaped apertures. Further,in the case in which light source images formed on predetermined onelens 11 on the lens array 12 are spaced apart from each other, aconstitution may be adopted in which a light source image, which isformed by the lens 9′ separate from the predetermined lens 9corresponding to the predetermined lens 11, is formed between lightsource images which are formed on the predetermined lens 11 in the samemanner as described above. In such a case, the same effect as describedabove can be obtained.

In addition, in FIG. 1, behind the lens array 12, the lens 13 isillustrated as the optical means of matching light to a shape of thelight-receiving surface 14 side, which should be illuminated, andconverting the light into illumination light having uniformity. However,as a structure of the illumination device of the present invention, theillumination device may have a structure without the lens 13, astructure in which plural single lenses are combined, or a structure ofan optical system in which optical elements such as a mirror and a prismare included.

Further, in the above-described illumination device, as shown in FIG. 8,if a liquid crystal panel 61 (optical modulation device) of atransmission type and a projection lens 62 are provided as an example ofthe display device of the present invention, a projection displayapparatus, which can provide a projection image with high uniformity,can be obtained.

Moreover, in FIG. 8, a structure including only one liquid crystal panel61 as an optical modulation device is illustrated. However, a structureincluding plural optical modulation devices may be adopted. In addition,instead of the liquid crystal panel 61 of the transmission type, atransmission light bulb, a reflection light bulb, a mirror panel whichcan change a direction of reflection with a micro-mirror arranged inarray, an optical modulation device of an optical writing system, animage display device, or the like can be used. Moreover, it isconceivable that the display device of the present invention is, forexample, a sheet for an OHP.

Further, in FIG. 1, the structure using the two light sources isillustrated. However, a structure using three or more light sources maybe adopted. However, in the case in which three or more (N) lightsources are used, the number of lenses NLA2 of the lens array 12 onlyhas to satisfy the following relation with respect to the number oflenses 9 NLA1 of he lens array 10:NLA 1 <NLA 2 <N×NLA 1  (Expression 4)In that case, the structure only has to be a structure in which the lensarray 10 is formed such that, in a first predetermined space which is alargest space among plural images formed on the lens array 12 by thepredetermined lens 9 of the lens array 10, a largest image among imagesformed on the lens array 12 a second predetermined space, which issmaller than the first predetermined space, apart from each other by thelens 9′ separate from the predetermined lens 9 of the lens array 10 isformed.

Moreover, although not shown in the figure, a structure using a prism, afilter, a mirror, or the like, which can perform color separation andcolor composition, may be adopted.

INDUSTRIAL APPLICABILITY

According to the illumination device and the illumination method inaccordance with the present invention, efficiency of use of plural lightsources can be improved. Thus, the illumination device and theillumination method are useful in a projection display apparatus and thelike.

1. An illumination device comprising: plural light sources; reflectingmeans having a reflection surface of reflecting light, which isirradiated from said plural light sources, in predetermined directionsin association with the respective light sources; a first lens arrayhaving plural lenses which are arranged a predetermined space apart fromsaid reflecting means; and a second lens array having plural lenseswhich are arranged a predetermined space apart from said first lensarray, wherein said first lens array is formed such that images of saidplural light sources are formed a predetermined space apart from eachother on lenses, which corresponds to predetermined lens of said firstlens array, among the plural lenses of said second lens array by lightfrom said plural light sources having passed the predetermined lens ofsaid first lens array, and all or a part of plural images formed byanother lens different from said predetermined lens of said first lensarray are arranged substantially among said formed images of said plurallight sources, and said second lens array is formed such that lightbeams forming light source images on said second lens array illuminate alight-receiving surface in a predetermined relation.
 2. The illuminationdevice according to claim 1, wherein said another lens of said firstlens array is formed to be decentered such that all or a part of pluralimages formed by said another lens are arranged among plural imagesformed on said second lens array by the predetermined lens of said firstlens array.
 3. The illumination device according to claim 2, whereinsaid second lens array is formed such that the images formed on saidsecond lens array via said another lens of said first lens array areguided to an area, which is to be illuminated, of said light-receivingsurface.
 4. The illumination device according to claim 3, wherein saidsecond lens array is formed without a center of curvature of lenses, onwhich the images formed via said another lens of said first lens arrayare formed, on said second lens array being changed substantially. 5.The illumination device according to claim 4, wherein the plural lenses,on which the images formed via said another lens of said first lensarray, on said second lens array are arranged across at least one lenson which the images formed via said predetermined lens of said firstlens array.
 6. The illumination device according to claim 5, whereinsaid plural light sources comprise a first light source and a secondlight source, said second lens array includes a first lens, a secondlens, a third lens, and a fourth lens, the first lens and the third lensof illuminating images, which have passed through the predetermined lensof said first lens array, on said light-receiving surface are formed onsaid second lens array, the second lens and the fourth lens ofilluminating images, which have passed through said another lens of saidfirst lens array, on said light-receiving surface are formed on saidsecond lens array, a center of curvature of said first lens and a centerof curvature of said third lens substantially coincide with each otherto form a first center of curvature, and a center of curvature of saidsecond lens and a center of curvature of said fourth lens substantiallycoincide with each other to form a second center of curvature differentfrom said first center of curvature, and said first lens, said secondlens, said third lens, and said fourth lens are arranged in this order.7. The illumination device according to claim 1, wherein, in said secondlens array, an aperture of a lens close to an optical axis is formedlarger than an aperture of a lens distant from the optical axis, and anaperture of a lens distant from the optical axis is formed smaller thanan aperture of a lens close to the optical axis.
 8. The illuminationdevice according to claim 1, wherein said first lens array is formedsuch that, in a first predetermined space which is a largest space ofspaces among plural images formed on said second lens array by thepredetermined lens of said first array, a largest image among imagesformed on said second lens array with a second predetermined space,which is smaller than said first predetermined space, apart from eachother by said another lens of said first lens array is arranged.
 9. Theillumination device according to claim 8, wherein said plural lightsources comprise a first light source and a second light source, andsaid first lens array is formed such that a value obtained by dividing awidth of an image according to a first light source, which is formed bythe predetermined lens of said first lens array, by said secondpredetermined space is equal to or larger than a value found by dividinga width of an image according to a second light source, which is formedby said another lens of said first lens array, by said firstpredetermined space.
 10. The illumination device according to claim 1,further comprising a display device of providing video information,which is arranged a predetermined space apart from said second lensarray, between said second lens array and said light receiving surface.11. An illumination method comprising: a step of reflecting lightirradiated from plural light sources in predetermined directions withreflecting means in association with the respective light sources andguiding the light to a first lens array having plural lenses which isarranged a predetermined space apart from said reflecting means; a stepof guiding the light from said plural light sources, which has passedthrough a predetermined lens of said first lens array, onto a lenscorresponding to said predetermined lens among plural lenses of a secondlens array having plural lenses which is arranged a predetermined spaceapart from said first lens array and forming images of said plural lightsources with a predetermined space apart from each other; a step offorming said first lens array such that all or a part of plural images,which are formed by another lens different from said predetermined lensof said first lens array, are arranged substantially among said formedimages of said plural light sources; and a step of forming said secondlens array such that images formed on said second lens array areilluminated on a light-receiving surface in a predetermined relation.